1. Technical Field
The present invention relates to a piezoelectric drive device and a robot.
2. Related Art
A piezoelectric actuator (piezoelectric drive device) which causes a piezoelectric element to vibrate a vibrating body so as to drive a driven body (driven member) has been used in controlling various operations for various devices. For example, JP-A-2010-16978 discloses that a frequency within a frequency range in which respective drivable frequencies overlap each other is employed as a simultaneous drive frequency, in a case where a plurality of ultrasonic motors (piezoelectric actuators) having respectively different resonance frequencies are simultaneously driven.
If a resonance frequency of a piezoelectric actuator is likely to be deviated due to a load or temperature change and the resonance frequency is deviated, a drive characteristic (an impedance characteristic, an amplitude characteristic, or the like) is unavoidably deviated in a drive frequency (normally, set to be the resonance frequency or to be in the vicinity of the resonance frequency) of the piezoelectric actuator. In addition, if a vibrating body is configured to include a member having less damage, a mechanical quality factor (Qm) of the vibrating body increases, and a Q-value (quantity representing resonance sharpness) increases consequently. Accordingly, the drive characteristic varies greatly in the drive frequency due to the deviated resonance frequency. For example, in a case where a substrate made of silicon (Si) is used as the vibrating body, the Q-value tends to increase. Thus, the substrate tends to considerably receive the influence of the varied drive characteristic. Furthermore, in a case where a plurality of piezoelectric actuators are simultaneously driven, respective resonance frequencies are less likely to be coincident with each other, and the respective drive characteristics are less likely to be aligned with each other. Therefore, in order to drive a driven unit by using the plurality of piezoelectric actuators having respectively different resonance frequencies, it is desirable to restrain the influence of the varied drive characteristic.
JP-A-2010-16978 has no consideration of an issue that the drive characteristic of the respective actuators is unavoidably varied in the drive frequency due to the respectively deviated resonance frequencies resulting from a load or temperature change.